This invention relates to a method for testing the authenticity of a data carrier according to the preamble of claim 1.
A method of this kind is known e.g. from EP 0 313 967 A1. In this method the physical structure of the integrated circuit is influenced selectively during chip production and the integrated circuit thus provided with certain features which are evaluable as physical properties characteristic of the circuit. In this connection this print proposes providing the integrated circuit with a metallic coating having a random surface structure which is scannable at several places via a resistance measurement, the thus obtained resistance profile being stored in the form of characteristic data for determining the authenticity of the data carrier. However, the detection of such a random surface structure is elaborate and difficult in terms of measurement technology
WO 94/15318 likewise discloses a method according to the preamble of claim 1. In this known method the physical property for testing the authenticity of a data carrier is determined from an irreversibly adjustable electric state of a circuit separately present on the integrated circuit. The electric property of the circuit is used for producing a characteristic value for the data carrier and evaluated for determining authenticity. Although the irreversibly adjusted electric state characteristic of the integrated circuit is easy to detect in terms of measurement technology, this test method requires additional circuit complexity in order to permit the authenticity of the data carrier to be tested.
The problem of the invention is to propose a method for testing the authenticity of a data carrier which permits reliable authenticity testing with low technical effort.
This problem is solved according to the invention by the features stated in claim 1.
The basic idea of the invention is to provide in at least one area of the integrated circuit of the data carrier a material which is energetically excitable, at least one characteristic property of the electromagnetic radiation emitted by the material being measured and evaluated for determining the authenticity of the data carrier. Since measurement is done contactlessly in the inventive method, authenticity can be tested independently of the data exchange defined in a transmission protocol.
The excitation is preferably effected by an electromagnetic radiation supplied to the material externally, the radiation emitted by the material being measured optically. However, the material can also be excited by an electric field produced by means provided on the integrated circuit of the data carrier. According to a development, the measured electromagnetic radiation can be converted into a binary value characteristic of the integrated circuit which can be stored in a memory of the integrated circuit. If the binary characteristic value derived from the measured electromagnetic radiation correlates with the characteristic value read from the memory of the data carrier, the integrated circuit and thus the data carrier are recognized as authentic. The resident characteristic value can additionally be linked in the integrated circuit of the data carrier with variable information transmitted to the data carrier from an external device, e.g. a random number produced by the device, to form output information and transmitted to the device, then being evaluated by the device for determining the authenticity of the data carrier.
One preferably uses a semiconductor material such as porous silicon that is monolithically integrable into the integrated circuit. For the physical properties of porous silicon, reference is made to the content of the literature xe2x80x9cPorous Silicon; A silicon structure with new optical properties,xe2x80x9d F. Buda and J. Kohanoff, in Prog. Quant. Electr. 1994, Vol. 18, pages 201-227. This literature describes in detail the laws underlying the luminescence of porous silicon. One can of course also use other semiconductor materials (e.g. doped manganese sulfide or cadmium sulfide) which have the property of emitting, when suitably excited, a characteristic electromagnetic radiation which is detectable by measurement technology.
However one can also use, rather than semiconductor materials, e.g. the polymer polyphenylene vinylene (PPV) which emits light when excited by an electric field. This polymer can be applied e.g. in the form of a photoresist to a silicon layer during production of the integrated circuit. The silicon layer forms one of the two electrodes between which the polymer is disposed. The second electrode can be e.g. a metal electrode. The silicon layer with the polymer and also the metal electrode can be covered by a passivating layer. One can also use other suitable materials which have the property of emitting, when suitably excited, an electromagnetic radiation which is characteristic of the material. These materials can be applied to a layer of the integrated circuit e.g. dispersed in lacquers or foils.
By providing a material on the integrated circuit which emits a characteristic electromagnetic radiation when suitably excited, one greatly impedes any simulation or manipulation of data carriers with such an authenticity feature since the production of an integrated circuit with such a material requires a high measure of knowledge and technical skill in the field of semiconductor technology.